Create an IIS website from a command line (or cscript)?

This method works on Windows Server 2003 IIS 6.0:

strComputer = "."
Set objWMIService = GetObject _
    ("winmgmts:{authenticationLevel=pktPrivacy}\\" _
        & strComputer & "\root\microsoftiisv2")

Set objWebService = objWMIService.ExecQuery _
    ("Select * From IISWebService")

arrBindings = Array(0)
Set arrBindings(0) = _
    objWMIService.Get("ServerBinding").SpawnInstance_()
arrBindings(0).IP = "192.168.1.1"
arrBindings(0).Port = "80"
arrBindings(0).Hostname = "www.example.com"

For Each objItem in objWebService
    objItem.CreateNewSite "Test Site", arrBindings, _
        "c:\inetpub\wwwroot\testsite"
Next

Here is the link to the Microsoft TechNet Script Repository related to or Managing Web sites on Internet Information Server 6.0.

Another useful TechNet article explains how to create an AppPool programmatically.

Here is an alternative method, which works on Windows Server 2000 (IIS 5.0) too. Write a .vbs file:

IISWebName = "Name of the Web"
IISWebPath = "D:\Websites\MyWeb"
IISWebHeader = "http://www.example.com"
IISIPAddress = "10.0.0.10"

Set wsShell = CreateObject("WScript.Shell") 
wsShell.Run "iisweb.vbs /create """ & IISWebPath & """ """ & IISWebName & """ /b 80 /i """ & IISIPAddress & """" /d """ & IISWebHeader & """"

If you want to add virtual directories, you could do it this way:

oShell2.Run "iisvdir.vbs /create """ & IISWebName & """ pfengine ""D:\Common\engine"""

You'll probably want to customise the website as well rather than leaving at its default settings. After much scrabbling around, this is what I came up with:

Sub CreateWebsite(name, hostName, physicalPath)
    ' Make connections to WMI, to the IIS namespace on the local machine. Then grab a reference to the WWW service 
    Dim locatorObj : set locatorObj = CreateObject("Wbemscripting.SWbemLocator") 
    Dim providerObj : set providerObj = locatorObj.ConnectServer(".", "root/MicrosoftIISv2") 
    Dim serviceObj : set serviceObj = providerObj.Get("IIsWebService='W3SVC'") 

    'Create a new instance as per splattne's answer
    Dim Bindings : Bindings = Array(0) 
    Set Bindings(0) = providerObj.get("ServerBinding").SpawnInstance_() 
    Bindings(0).IP = "" 
    Bindings(0).Port = "80" 
    Bindings(0).Hostname = hostName

    ' Create the new Web site using the CreateNewSite method of the IIsWebService object. 
    Dim newSitePath : newSitePath = serviceObj.CreateNewSite(name, Bindings, physicalPath) 

    ' CreateNewSite returns a string reference to the created web service. To alter the settings we need to create a string which references the root virtual directory settings.
    Dim settingsPath : settingsPath = Replace(Left(newSitePath, Len(newSitePath) - 1) & "/ROOT'", "IIsWebServer","IIsWebVirtualDirSetting")

    ' Grab a reference to the settings
    Dim settings : set settings = providerObj.get(settingsPath)

    ' By comparing the settings of an existing, manually set up site, and one created with Splattne's method I realised I needed to change the following
    settings.AspEnableParentPaths = True
    settings.AccessFlags = 512
    settings.AccessRead = True
    settings.AuthAnonymous = True
    settings.AuthFlags = 5
    settings.AuthNTLM = True
    settings.AccessScript = True
    settings.AppFriendlyName = name
    settings.Put_()

    ' Set a custom handler for 500 errors. In this case a url called 500.asp. This is a bit hacky but it works.
    settings.HttpErrors(41).Properties_("HttpErrorCode") = 500
    settings.HttpErrors(41).Properties_("HttpErrorSubcode") = "*"
    settings.HttpErrors(41).Properties_("HandlerType") = "URL"
    settings.HttpErrors(41).Properties_("HandlerLocation") = "/500.asp"
    settings.Put_()

    ' Start the service
    Dim newSite: set newSite = providerObj.Get(newSitePath)
    newSite.Start
End Sub

I think PowerShell is really for IIS 7. Are you sure you want IIS 6 and not IIS 7? IIS 7 has the appcmd command which is somewhat difficult to use but works.